This invention relates to apparatus and method for effecting reciprocation of a piston, and especially to such apparatus for effecting linear reciprocatory motions of a piston with a dwell time at the end of each direction of reciprocation, the dwell time preferably being the same at both ends of the stroke and controllably adjustable.
There are a large number of applications in which it is desirable to produce controlled reciprocation of a piston by means of fluid pressures applied alternately to opposite ends of the piston. In certain cases it is also desired that the piston dwell in one or both of its two end positions, and in some cases that these dwell times be controllably adjustable. Such uses commonly arise, for example, in connection with assembly line production and product handling equipment, wherein the piston is advanced to move an object into a measurement position, remains in that position during the measurement, is retracted to permit the object to be moved out of the measurement station, and remains in the retracted position sufficiently long for the next object to move into position in the measurement station.
One application of such apparatus with respect to which the invention will be particularly described is in the testing of bottle closures. For example, my copending application Ser. No. 475,113, filed May 31, 1974, illustrates a situation in which the thickness of a membrane at the center of a bottle closure is measured by moving the closure against the protruding end of the probe of a fluidic thickness-checking device to check whether this thickness is within or outside of permissible tolerances. In this application, successive stoppers are moved into position against the sensor probe by means of a supporting piston which is first retracted to permit the closure to move into position at the measuring station; is then advanced to move the closure forward into a reference position against the sensor probe; remains or dwells in this position while the measurement is made and the results indicated or used to control automatic reject equipment; and is then retracted and left in its retracted position while the just-tested closure moves out of the measurement station and the next closure moves into position in the station.
It is also desirable in some cases that the reciprocating piston reverse its motion, e.g. change from its advancing stroke to its retracting stroke, whenever the piston motion is arrested, whether or not it has completed its maximum possible stroke.
Accordingly it is an object of the invention to provide a new and useful apparatus and method for effecting reciprocation of a piston.
It is also an object to provide such apparatus and method in which the reciprocation of the piston is provided with a substantial dwell time at least at one end of its stroke.
A further object is to provide such a dwell time at both ends of said stroke.
It is also an object to provide such apparatus and method in which the dwell times at both ends of the stroke are controllably adjustable from a single common control.
It is also an object to provide such a method and apparatus in which the piston motion will automatically reverse itself whenever its motion is arrested, regardless of whether it has completed its maximum stroke.
It is also an object to provide such apparatus which is controlled by fluidic means.
A further object is to provide such method and apparatus which is small, inexpensive, and consistent in its operation.
A further object is to provide such apparatus and method which supplies external fluidic indication of the direction of reciprocation of the piston at any time.